Investigation of pushover analysis procedures for reliability-based and performance-based seismic design with applications to asymmetric building structures

In 1995, a framework for a reliability-based, performance-based seismic design procedure was proposed by Collins. The basic idea behind the procedure was to develop an equivalent single-degree-of-freedom (SDOF) model of the structure and then to use this model and uniform hazard spectra to predict maximum displacements and drifts in the multi-degree-of-freedom (MDOF) structure. Deterministic design-checking equations based on the equivalent SDOF system were developed, and design factors (analogous to load and resistance factors) were calibrated and used in design-checking equations to account for the uncertainty in the equivalent SDOF model, the seismic environment, and site soil conditions. The parameters of the SDOF model were obtained using information from two-dimensional static pushover analyses of the lateral force resisting systems of the structure.; The objective of this research was to enhance or improve procedure by looking at alternative ways in which pushover analyses could be used. Specifically, this thesis looks at the following two topics: (1) The choice of the lateral force distribution is one of the most important aspects of such analyses since any single lateral force pattern may not capture all deformation characteristics. This is especially true when nonlinear behavior of the structure is considered. In the original procedure, only one force distribution was considered. This dissertation summarizes the results of a study to evaluate several possible force distributions. (2) The design procedure proposed by Collins was based on static pushover analyses of a two-dimensional model of a building. Such analyses are acceptable if buildings are regular and symmetric or if torsional effects can be otherwise accounted for. In this dissertation, the design procedure is extended to three-dimensional cases to explicitly account for the torsional behavior of asymmetric building structures.